<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>圆环</title>
    <style>
        .annulus{
            width: 100px;
            height: 100px;
            border-radius: 50%;
            background-color: greenyellow;
            border: 5px solid red;
            padding: 10px;
            background-clip: content-box;
        }
    </style>
</head>
<body>
    <div class="annulus"></div>
</body>
</html>